First of all, it is a government, not like they are a company that can go bankrupt, they are there, they may not be able to pay right now, but that doesn't mean that you can't give them any loans in the future because they may get better after this situation. Secondly, we are talking about having some debt even after this, they are not reaching to zero, they are defaulting on some debt, but they still have some more debt left that they will pay, which will help them gain some credit again.
No, they are not paying anything. Theoretically, they are bankrupt because they have a large sum of debt that they need to pay but they don't have that much reserve left. Their loan is more than 70% of their reserve and you are talking about getting better in time. But how they will do that when they can only offer trade through their native currency which no one will accept. International trade is mostly done with USD which they do not have right now.
No companies will occupy and sell their natural resource to get back their loan. Sri Lanka can not pay their debt by itself but lender by organizations and countries will take it anyway. So the only losing side is Sri Lanka.